1. Field of the Disclosure
Embodiments of the present disclosure relate generally to complementary metal-oxide-semiconductor (CMOS) fabrication and more specifically to the fabricating of a light pipe for a CMOS image sensor.
2. Description of the Related Art
Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Image sensors have great usages in many fields. CMOS image sensors generally consume less power and also cost less than charge-coupled devices (CCD) image sensors. As the resolution of a CMOS image sensor increases, the size of each pixel sensor in the image sensor shrinks, which may also lead to the decreasing of the size of the photosensitive element (e.g., photodiode) in each pixel sensor. As the CMOS image sensors become increasingly more sophisticated, the requirements of pixel sensitivity and angular response for each pixel sensor also increase due to increasing aspect ratio of stack height to pixel pitch.
One of the methods to improve light sensitivity and angular response of the pixel sensor is to implement a light pipe (LP) on top of the photodiode. However, conventional LP fabrication processes often lead to depth fluctuations and size variations for the LPs in the CMOS sensor. The LPs built by these conventional fabrication processes may lead to low quality pixel sensors having poor light sensitivity and poor angular response.